Survey of the population of eider ducks in the Wadden Sea of Lower Saxony in spring 2001. Since 1986, populations of eider ducks in the Wadden Sea of Lower Saxony have been recorded twice a year from an airplane during a tide. These are the moulting (July/August) and overwintering (January/February) stocks. The counts take place in coordination with Schleswig-Holstein. The data is part of the Trilateral Monitoring and Assessment Program (TMAP). Monitoring of migratory birds (Eiders) in the Wadden Sea of Lower Saxony in spring 2001. The population of migratory birds (Eiders) in Lower Saxony's Wadden Sea is determined biyearly by aerial flight since 1986. Counts are carried out in July/August during the moult and in January/February and are coordinated with Schleswig-Holstein. The data are part of the trilateral monitoring and assessment program (TMAP).